AP Psychology Unit 1 (Biological Bases of Behavior): Biological Bases Study Notes

Central nervous system (CNS)

The brain and spinal cord; the main control center where information is integrated and decisions are made.

Peripheral nervous system (PNS)

All nerves outside the CNS that carry sensory information to the CNS and motor commands from the CNS, connecting the CNS to the rest of the body.

Reflex arc

The fast neural pathway for a reflex: receptor detects a stimulus → sensory neuron to spinal cord → interneurons route the signal → motor neuron activates muscles, often before conscious awareness.

Somatic nervous system

The PNS division that controls voluntary skeletal muscle movements and carries sensory information to the CNS.

Autonomic nervous system (ANS)

The PNS division that regulates involuntary functions such as heart rate, digestion, and pupil dilation; strongly involved in stress and emotion.

Sympathetic nervous system

ANS branch that arouses the body for action (fight-or-flight), increasing heart rate and airflow and inhibiting digestion.

Parasympathetic nervous system

ANS branch that calms the body and conserves energy (rest-and-digest), decreasing heart rate and stimulating digestion.

Afferent (sensory) nerves/neurons

Neural pathways that carry sensory information toward the CNS (Afferent Arrives at the CNS).

Efferent (motor) nerves/neurons

Neural pathways that carry motor commands away from the CNS to muscles and glands (Efferent Exits the CNS).

Electroencephalogram (EEG)

A recording of the brain’s electrical activity via electrodes on the scalp; especially useful for timing (e.g., sleep stages), with limited ability to pinpoint deep sources.

MRI (magnetic resonance imaging)

A brain-imaging method that produces detailed structural images of soft tissue (anatomy).

fMRI (functional MRI)

A method that measures brain activity indirectly via blood flow/oxygenation changes, combining functional information with spatial detail.

PET (positron emission tomography) scan

An imaging method that shows brain activity by tracking glucose/metabolic processes (often using a tracer), useful for comparing activity patterns across tasks.

Medulla

A brainstem structure that controls vital survival functions such as heartbeat and breathing.

Reticular formation

A brainstem network involved in arousal, alertness, and filtering incoming stimuli (important for consciousness and attention).

Cerebellum

A brain region involved in balance, coordination, fine motor control, and often linked to procedural (skill) memory.

Thalamus

A sensory relay hub that routes most sensory information (except smell) to appropriate areas of the cerebral cortex.

Amygdala

A limbic structure that helps process emotional significance—especially threat-related cues; important in fear and aggression.

Hippocampus

A limbic structure crucial for forming and consolidating new explicit (declarative) memories.

Hypothalamus

A brain structure that regulates drives and homeostasis (hunger, thirst, temperature) and links the nervous system to the endocrine system by controlling the pituitary gland.

Broca’s area

A (typically left) frontal-lobe language area involved in speech production; damage often causes slow, effortful speech (Broca’s aphasia).

Wernicke’s area

A (typically left) temporal-lobe language area involved in language comprehension; damage often causes fluent but nonsensical speech with poor understanding (Wernicke’s aphasia).

Action potential

A brief electrical impulse that travels down a neuron’s axon once threshold is reached; follows an all-or-none pattern and varies mainly by firing rate, not size.

Neurotransmitter

A chemical messenger released from axon terminals into the synaptic cleft that binds to receptors on another neuron, producing excitatory or inhibitory effects.

Endocrine system

The body’s slower, longer-lasting chemical communication system in which glands release hormones into the bloodstream, influencing states like stress, mood, energy, and motivation.